Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3977061 A
Publication typeGrant
Application numberUS 05/504,819
Publication dateAug 31, 1976
Filing dateSep 10, 1974
Priority dateSep 17, 1973
Also published asDE2443160A1, DE2443160B2, DE2443160C3
Publication number05504819, 504819, US 3977061 A, US 3977061A, US-A-3977061, US3977061 A, US3977061A
InventorsJan Nils Lindstrom, Fall Johan Olof William Ohlsson
Original AssigneeSandvik Aktiebolag
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Cutting insert and method of making the same
US 3977061 A
Abstract
The wear resistance and toughness of a cutting insert comprising a ceramic oxide is improved by applying to it a thin surface layer of ceramic oxide, deposited from a gaseous phase, in which surface layer the grains have a size smaller than 1 micron and preferably smaller than 0.5 micron.
In effecting the deposition, at least one of the components of the gaseous phase is present therein in the highest concentration possible without formation of powder.
Images(2)
Previous page
Next page
Claims(2)
We claim:
1. A cutting insert for chip-forming machining said insert consisting of a sintered substrate of of at least one wear-resisting ceramic oxide or of wear-resisting ceramic oxide mixed with at least one hard carbide or nitride and binder metal, on which substrate is a wear-resisting ceramic oxide surface layer consisting of an oxide from of the group consisting of Al, Zr, Si, Ca, Mg, Ti and Hf, the surface layer having been deposited from a gaseous phase and having a thickness of 0.5-100 μm, its mean grain size being smaller than 1 μm and essentially smaller than is the mean grain size of the sintered substrate.
2. A cutting insert according to claim 1, in which a thin and extremely fine-grained intermediate layer of a material is applied between the thin surface layer consisting of wear-resisting ceramic oxide and the essentially ceramic substrate, said intermediate layer consisting essentially of a member of the group consisting of carbides and nitrides of Ti. Zr, Hf, V, Nb, Ta, Cr, Mo, W, Si and B.
Description

The present invention relates to a cutting insert consisting essentially of ceramic oxides and, in particular, to a cutting insert having thin, extremely fine-grained surface layer. The invention also deals with a method of manufacturing said insert.

Many different methods of making ceramic cutting inserts have previously become known. For example, solids bodies of ceramic oxides -- usually consisting of Al2 O3 with optional addition of other oxides as for example TiO or MgO -- have been prepared by a sintering technique. Also, cutting inserts of composite or semi-ceramic type are well known, the ceramic material (of oxide) being mixed with one or more hard carbides, nitrides or the like or with binder metal. The essential reason for such additions of admixtures has been to improve the toughness or strength, and more precisely the toughness considered in the macro- as well as in the micro- scale. Thus, cutting inserts of sintered aluminum oxide do not have particularly good resistance to wear of the clearance face or to cratering, if the potential capacity is taken into consideration.

It has been found, however, that the wear resistance is increased if the grain size of the aluminum oxide is made as small as possible. Furthermore, to obtain a good cratering resistance it is necessary that the grains are strongly bonded to each other or to other present materials. It is difficult, however, to meet both of said requirements, because a good binding or bond demands high sintering temperature, which latter customarily has the disadvantage that it increases the grain size.

An important reason for the previously encountered unsatisfactory toughness and wear resistance is thus the fact that it has not been possible to reduce the grain size of ceramic cutting inserts sufficiently, which means a lowest limit of about 2 μm (microns) mean grain size. As indicated before, it is known that a cutting edge consisting of large grains is broken down more readily than a cutting edge consisting of smaller grains. Ceramic inserts are normally worn out by the breaking of their cutting edges.

A radical solution of the problem of reducing the grain size to desired level has now been found in an unexpected and surprising way. The new method is based upon the technique of applying thin ceramic surface layers having extremely small grain size upon a ceramic substrate or cutting insert. In applying the layer by means of deposition from a gaseous phase (i.e., so-called "CVD"-methods ["Chemical Vapor Deposition"]), it is possible to reduce the grain size below 1 μm. Furthermore, said deposition includes or builds up the cutting edge area where the fine grained material is needed. The grain size is preferably reduced to <0.5 μm. By means of the invention, even a substrate having very good macroscale toughness (being for example of mixed ceramic type) can be used without any reduction of wear resistance and strength.

It has been found that thin ceramic layers, being composed of Al2 O3, for example, having a thickness of 0.5-100 μm (and preferably 1-8 μm) are sufficient to give the desired effect regarding both the cutting edge strength or toughness and the wear resistance. The substrate advantageously may be a ceramic, essentially Al2 O3, sometimes having improved "macro toughness" by alloying with binder metal.

It previously had been proposed to make solid bodies of ceramic material by means of CVD-technique. This method is very expensive, however. It is also particularly difficult, if not impossible, to make sharp cutting edges by said technique. Furthermore, a high deposition rate has to be used for economical reasons, which means that the grain size of the material will be relatively coarse. It is possible, however, also to coat such bodies having pure CVD-character beneficially by means of the invention, for example by changing over to conditions giving a fine-grained structure at the end of the CVD-coating. In most cases, however, a forming or shaping operation would be necessary before the fine grained layer could be applied.

There also previously had been known other methods of coating with oxides, in which have been mentioned incidentally that ceramic materials may be coated with stable oxides including Al2 O3. Known cases relate to coating by means of flame spraying, however, in which the grain size cannot be reduced as by a CVD-method. Furthermore, the layers could not be made so thin or uniform by said methods that a following working or finishing could be avoided. Thus, the known methods do not at all deal with the concept of using the same material in substrate and layer, at which for example only the grain size is different.

The coated inserts according to the invention can thus be manufactured according to methods known per se. The substrate is normally manufactured by pressing and sintering technique and thus the surface layer is applied by means of deposition from a gaseous phase. To obtain a particularly fine grain size it is urgent to have the highest possible over-saturation in the gas, without driving the over-saturation so far that a formation of powder will occur. (Over-saturation is present when the beginning concentrations of reactants and products -- ordered as in an equilibrium equation -- are greater than the equilibrium concentrations ordered in an analogous way.)

Another method of preparing a particularly fine-grained layer of ceramics is to deposit -- as an intermediate step -- a thin, extremely fine-grained layer of hard carbide and/or nitride,-- for example, TiC. This intermediate layer reduces the grain size of the ceramic layer applied upon said intermediate layer, in an epi-taxy way (said method thus means that the crystal structure of the ceramic layer will be adapted to the structure of the substrate, in this case the intermediate layer). Among hard principles which have been found particularly suitable to form an intermediate layer are carbides and/or nitrides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Si and/or B.

Besides Al2 O3, the ceramic layer can also consist of an oxide of Zr, Si, Ca, Mg, Ti and/or Hf. Such layers can also be applied in combination or upon each other, depending upon different demands or possibilities.

The method used in preparing ceramic cutting inserts according to the invention will now be described by illustrations in the following examples 1-4, and with reference to the attached drawings which show:

FIG. 1, principle sketch of an apparatus for depositing surface layers;

FIG. 2, principle sketch of an alternative detail in the apparatus according to FIG. 1.

The apparatus sketched in FIG. 1 illustrates the use of a chlorinating reactor 25 for chlorination of Al, for example, in the form of grains 26. For this purpose hydrogen from a gas source 1 is mixed by conduits 19, 20 with chlorine alternatively hydrochloric acid from a source 17 and the mixture is led to the chlorinating reactor through a conduit 21. The gas mixture from the chlorinating reactor 25 is then mixed with hydrogen and carbon monoxide and carbon dioxide from the gas source 18 respectively 28. The resulting mixture is then led to the coating reactor 11 by the valve-equipped conduit 27.

The apparatus shown in FIG. 2 has gas sources, for example gas tubes 1, 2 for supply of hydrogen respectively methane and/or nitrogen. The conduits 3 and 4 from the respective sources combined into a conduit 5, by which latter the gas mixture is led to a vessel 6 in which a metal halide (for example TiCl4) is heated to vaporization, the resulting composite gas being led to the reactor 11 by a common conduit 9. The gas mixture passes a heat exchanger 7 controlled by a thermostat 8 for setting the content of TiCl4 in the gas. In the reactor 11, being heated by means of a furnace 11, the substrate is placed for coating. From the reactor vessel 11 the gas is sucked out, passing a valve-equipped conduit 12 and a cool trap 13. The evacuation of gas from the system is done in a conduit 14 by means of a vacuum pump 15 having an outlet 16. (In the drawings, purification means for gas have been omitted.)

In the following examples 1-4 there are given those conditions under which ceramic cutting inserts according to the invention have been prepared. In the examples 5-6 there are results which have been obtained in cutting tests.

EXAMPLE 1

A ceramic cutting insert, consisting of Al2 O3 with an addition of MgO, was coated with a thin surface layer of Al2 O3. The mean grain size of the substrate or the ceramic cutting insert was about 5 μm. The coating was performed by means of CVD-technique, in which a conversion took place essentially between aluminum chloride, carbon dioxide and hydrogen according to the reaction: 2AlCl3 +3CO2 +3H2 →Al2 O3 +3CO+6HCl. The following conditions were used:

______________________________________Length of the coating operation:                7 minutesTemperature of the substrate:                1000C.Total pressure of the gaseous phase:                50 torr (mm Hg)______________________________________

Supplied amounts of gas (the volumes reduced to the temperature of 20 C. and the pressure of 760 torr):

______________________________________hydrogen:             200 cm3 /min.carbon containing gas:                 200 cm3 /min.aluminum chloride:    10 mg/min.______________________________________

The formed surface layer consisted essentially of alpha-aluminum oxide having a grain size of about 1 μm and had a thickness of about 1 μm.

EXAMPLE 2

Coating with a surface layer of Al2 O3 was performed in a reactor whose essential parts were made of a nickel alloy. In this reactor vessel 3000 sintered ceramic cutting inserts were heated to 1100 C. The inserts were made of Al2 O3 with a certain addition of TiO. The grain size was 2 μm. The inserts were placed on strainer-like plates so that a good contact with the surrounding gas would be obtained. The gas being a mixture consisting of 86% H2, 5% CO2, 4% CO and 5% Al2 O3, prepared in a way per se known was led to the reactor in a single conduit. The pressure in the reactor could be maintained at 15 torr (mm Hg) because the gas was sucked out of the reactor vessel by means of a vacuum pump protected from corrosive reaction products (for example HCl) by a cool trap with liquid nitrogen situated before the pump. In this way a linear gas flow rate of 3.5 m/sec. was obtained in the charge. Said treatment was continued for 3 hours. As a result extremely fine-grained and homogeneous surface layers were obtained. The grain-size was above 0.5 μm and the thickness of this surface layer was about 2 μm.

EXAMPLE 3

Coating with an intermediate layer of TiC was done according to a method analogous with the method described in Example 2. The substrate was 3000 sintered cutting inserts of mixed ceramic type consisting of Al2 O3 with additions of WC + Co. The mean grain size was about 7 μm.

The deposition gas -- consisting of a mixture consisting of 10% TiCl4, 8% CH4 and 82% H2 -- was prepared in known ways. The pressure in the reactor was maintained at 15 torr (mm Hg), and a linear gas flow rate of 1 m/sec. was maintained in the charge. Said treatment was continued for 30 minutes. As a result, there were obtained fine-grained, compact layers of TiC with a thickness of about 2 μm.

In a separate second step, the 3000 cutting inserts were treated in an equipment nearly identical with the apparatus earlier described. The gas supplying system was different, however, in that a gas having the composition 82% H2, 5% CO2, 8% CO and 5% AlCl3 could be dosed. The substrate temperature was 1100 C. and the pressure 15 torr. A linear gas flow rate of 3.5 m/sec. was used. After a coating time of 3 hours, 2 μm thick layers of Al2 O3 had been formed upon the TiC-coated cutting inserts. The bond of the Al2 O3 layer to the TiC layer was good and the grain size of the latter layer was <0.5 μm.

EXAMPLE 4

Coating of ceramic cutting inserts was effected with silicon dioxide in an apparatus of the same kind as in earlier examples. The substrate was ceramic inserts consisting of Al2 O3 with an addition of MgO. The mean grain size was about 5 μm.

In the apparatus where the treatment was carried out, the gas supply system had been modified so that a gas with the composition 70% H2, 5% CO2, 20% CO and 5% SiCl4 could be dosed. The substrate temperature was 1100 C. and the pressure was 15 torr. A linear gas flow rate of 3.5 m/sec. was maintained. After a treatment of 3 hours, 2 μm thick layers of SiO2 had been formed. The adherence of the SiO2 layer to the substrate was excellent and its grain size was <0.5 μm.

EXAMPLE 5

Test cutting by means of inserts made according to Example 2.

Conditions:

Turning of a brake drum (roughing of a flange)

Material: Steel with a hardness of HB 180

Tool: Insert holder "T-Max"

Insert type "SNGN 120812"

Primary land=0.2 mm 20

______________________________________Cutting data:Cutting speed:      328-288 m/minFeed:               0.49 mm/revCutting depth:      3 mmCriterion of wear:  insert failure______________________________________

Uncoated ceramics: 82 min

Coated ceramic according to Example 2: 122 min

Increase of production: about 50%

This test showed that a considerable increase in productivity can be obtained by means of the improved edge toughness.

EXAMPLE 6

Another cutting test by means of inserts prepared according to Example 2.

Conditions:

Turning of a brake drum (finishing)

Material: Alloyed steel with a hardness of HB 230

Tool: Insert holder "T-Max"

Insert type "SNUN 120424"

Primary land = 0.05 mm 20

______________________________________Cutting data:Cutting speed:      500 m/min.Feed:               0.21 mm/rev.Cutting depth:      1 mm______________________________________

Criterion of wear: Inferior surface finish

Uncoated ceramics: 17 min

Coated ceramics according to Example 2: 42 min

In finishing, the inserts coated according to the invention obtained an essentially increased life.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2943008 *Jul 17, 1956Jun 28, 1960Electro Refractories & AbrasivRefractory articles
US3014815 *Oct 16, 1958Dec 26, 1961Philips CorpMethod of providing articles with metal oxide layers
US3208873 *Jan 5, 1962Sep 28, 1965IbmMethod and apparatus for depositing films of refractory metal oxides and refractory metals
US3615275 *Dec 12, 1967Oct 26, 1971Texas Instruments IncHomogeneously fine-grained vapor-deposited material in bulk form
US3642522 *Jul 15, 1969Feb 15, 1972Suisse Horlogerie Rech LabMethod for producing hard coatings on a surface
US3692565 *Oct 22, 1970Sep 19, 1972Lersmacher BerndMethod of depositing substances from the gas phase
US3836392 *Jul 5, 1972Sep 17, 1974Sandvik AbProcess for increasing the resistance to wear of the surface of hard metal cemented carbide parts subject to wear
US3837896 *Nov 3, 1972Sep 24, 1974Sandvik AbSintered cemented carbide body coated with two layers
US3852098 *Dec 15, 1972Dec 3, 1974Ppg Industries IncMethod for increasing rate of coating using vaporized reactants
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4109050 *Dec 9, 1976Aug 22, 1978General Electric CompanyCoated silicon-based ceramic composites and method for making same
US4203690 *Sep 8, 1978May 20, 1980Ngk Spark Plug Co., Ltd.Ceramic cutting tip
US4323323 *Nov 5, 1979Apr 6, 1982Lucas Industries LimitedTool tip for a machine tool
US4352308 *Mar 10, 1980Oct 5, 1982Ford Motor CompanyMethod of cutting cast iron with Si3 N4 composite cutting tool material
US4357382 *Nov 6, 1980Nov 2, 1982Fansteel Inc.Coated cemented carbide bodies
US4440547 *May 20, 1982Apr 3, 1984Gte Laboratories IncorporatedAlumina coated silicon nitride cutting tools
US4525415 *Sep 8, 1982Jun 25, 1985Iscar LimitedSintered hard metal products having a multi-layer wear-resistant coating
US4608243 *Oct 17, 1985Aug 26, 1986Borg-Warner CorporationHigh hardness hafnium nitride
US4619865 *Oct 9, 1984Oct 28, 1986Energy Conversion Devices, Inc.Multilayer coating and method
US4720437 *Mar 21, 1986Jan 19, 1988Sumitomo Electric Industries, Ltd.Surface-coated cemented carbide article or part
US4724169 *Jun 24, 1986Feb 9, 1988Ovonic Synthetic Materials Company, Inc.Method of producing multilayer coatings on a substrate
US4745010 *Jan 20, 1987May 17, 1988Gte Laboratories IncorporatedProcess for depositing a composite ceramic coating on a cemented carbide substrate
US4749629 *Jan 20, 1987Jun 7, 1988Gte LaboratoriesUltrathin laminated oxide coatings and methods
US4749630 *Jun 30, 1986Jun 7, 1988Fried. Krupp Gesellschaft Mit Beschrankter HaftungCoated hardmetal body
US4751109 *Jan 20, 1987Jun 14, 1988Gte Laboratories IncorporatedA process for depositing a composite ceramic coating on a hard ceramic substrate
US4804589 *Oct 29, 1987Feb 14, 1989Ngk Insulators, Ltd.Silicon carbide sintered members
US4816349 *Oct 22, 1987Mar 28, 1989Ngk Insulators, Ltd.Zirconia-coated silicon nitride sintered member
US4835062 *Mar 5, 1986May 30, 1989Kernforschungszentrum Karlsruhe GmbhProtective coating for metallic substrates
US4882109 *Sep 19, 1988Nov 21, 1989Ngk Insulators, Ltd.Process of preparing zirconia-coated silicon nitride sintered member
US4890574 *Jun 14, 1988Jan 2, 1990Gte Laboratories IncorporatedInternal reactor for chemical vapor deposition
US4892792 *Aug 12, 1988Jan 9, 1990Gte Laboratories IncorporatedA1N coated silicon nitride based cutting tools
US4936959 *Dec 16, 1987Jun 26, 1990Ford Motor CompanyMethod of making cutting tool for aluminum work pieces having enhanced crater wear resistance
US4943450 *Dec 14, 1989Jul 24, 1990Gte Laboratories IncorporatedMethod for depositing nitride-based composite coatings by CVD
US4950558 *Sep 23, 1988Aug 21, 1990Gte Laboratories IncorporatedOxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof
US4965140 *Jun 14, 1988Oct 23, 1990Gte Laboratories IncorporatedComposite coatings on refractory substrates
US5026601 *Feb 29, 1988Jun 25, 1991Ngk Spark Plug Co., Ltd.Zirconia-base sintered bodies having coating films
US5487625 *Nov 30, 1993Jan 30, 1996Sandvik AbOxide coated cutting tool
US5543176 *Sep 30, 1993Aug 6, 1996Sandvik AbCVD of Al2 O3 layers on cutting inserts
US5630275 *Sep 1, 1995May 20, 1997Warner-Lambert CompanyMulti-blade razor head with improved performance
US5654035 *Sep 22, 1995Aug 5, 1997Sandvik AbMethod of coating a body with an α-alumina coating
US5702808 *Nov 14, 1995Dec 30, 1997Sandvik AbAl2 O2 -coated cutting tool preferably for near net shape machining
US5834061 *Jul 22, 1997Nov 10, 1998Sandvik AbAl2 O3 coated cutting tool preferably for near net shape machining
US6327784 *Dec 22, 1999Dec 11, 2001U.S. Philips CorporationMethod of manufacturing a cutting member having an auxiliary layer
US6333103 *Nov 5, 1999Dec 25, 2001Hitachi Metals, Ltd.Aluminum oxide-coated article
US7140113Apr 17, 2002Nov 28, 2006Lazorblades, Inc.Ceramic blade and production method therefor
US7587829Nov 28, 2006Sep 15, 2009Lazorblades, Inc.Ceramic blade and production method therefor
US20040163262 *Apr 17, 2002Aug 26, 2004King Rodney L.Ceramic blade and production method therefor
USRE32093 *Apr 9, 1984Mar 18, 1986General Electric CompanyAluminum oxide coated titanium-containing cemented carbide product
USRE32111 *Jul 29, 1983Apr 15, 1986Fansteel Inc.Coated cemented carbide bodies
USRE44870Aug 8, 2008Apr 29, 2014Sandvik Intellectual Property AbAluminum oxide coated cutting tool and method of manufacturing thereof
EP0106817A1 *Aug 12, 1983Apr 25, 1984Santrade Ltd.Cutting insert and method of making the same
WO1997018912A1 *Nov 22, 1995May 29, 1997Marcus Robert BKnifes blades having ultra-sharp cutting edges and methods of fabrication
WO2002083374A2 *Apr 17, 2002Oct 24, 2002Theodore C CrawfordCeramic blade and production method therefor
Classifications
U.S. Classification407/119, 428/336, 428/410, 428/212, 428/428, 428/213, 30/346.54, 428/698, 428/334, 428/697
International ClassificationC04B35/10, C23C16/448, C23C16/36, C23C16/34, C04B41/87, B23P15/30, B23B27/14, C23C16/40, C23C16/32, C04B35/00
Cooperative ClassificationC23C16/40, C23C16/403, B23P15/30, Y10T428/265, B23B27/148, C23C16/4488, Y10T428/263, C23C16/405, C23C16/32, Y10T428/24942, C23C16/36, Y10T407/27, Y10T428/315, Y10T428/2495, C23C16/34
European ClassificationC23C16/40D, B23P15/30, C23C16/448K, C23C16/40H, B23B27/14C, C23C16/34, C23C16/32, C23C16/40, C23C16/36
Legal Events
DateCodeEventDescription
Sep 14, 1982ASAssignment
Owner name: SANTRADE LTD., ALPENQUAI 12, CH-6002, LUCERNE, SWI
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SANDVIK AKTIEBOLAG, A CORP. OF SWEDEN;REEL/FRAME:004085/0132
Effective date: 19820908